Mechanism of antagonistic effects of Andrographis paniculata methanolic extract against Staphylococcus aureus

• الحاوية / القاعدة: Asian Pacific Journal of Tropical Medicine
• المؤلف الرئيسي: 2-s2.0-85026837792
• التنسيق: مقال
• اللغة: English
• منشور في: Elsevier (Singapore) Pte Ltd 2017
• الوصول للمادة أونلاين: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026837792&doi=10.1016%2fj.apjtm.2017.07.009&partnerID=40&md5=b572e7abec2c0c86b8fcdc060bfa63f6

Objective To investigate the effects of Andrographis paniculata (Burm.f.) Wall. Ex Nees (A. paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus (S. aureus) with respect to its survival in vitro. Methods Antioxidative property of methanolic leaves extract of A. paniculata (0.06 mg/mL). Minimum inhibitory concentration (MIC) was determined by its ability to reduce hydrogen peroxide (H2O2) toxicity against S. aureus ATCC 25923 (3.8 × 108 cfu/mL). Effects of the extract on expressions of katA (encoding catalase), sodA and sodM [encoding superoxide dismutases (SODs)], and ahpC [encoding alkylhydroperoxide reductase C (AhpC)] in S. aureus were determined by RT-qPCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction (NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O2− in S. aureus. Results Cells challenged with 7.5 mmol/L H2O2 showed 0% survival in 30 min whereas 25% survived after treatment with the extract and H2O2. Cells that were treated with the extract alone had 43% survival in the same exposure period. Expressions of sodA and sodM genes in extract-treated cells were lowered 0.8-fold and 0.7-fold, respectively with decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U (P < 0.05). In contrast, extract-treated S. aureus cells showed 3.3-fold increase in katA expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U, (P < 0.05). More profoundly, ahpC expression was increased 61-fold in extract-treated cells, (P < 0.05) with corresponding increase in AhpC activity of 0.018 U compared to untreated cells, 0.012 U, (P < 0.05). Extract-treated cells had significantly lower intra- and extracellular O2 − levels with absorbance readings (A575 nm) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928 (P < 0.05), respectively. Conclusions Taken together these results suggest that the low MIC of A. paniculata methanolic leaves extract (0.06 mg/mL) reduce H2O2 toxicity and more importantly, was in itself effectively inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sodA and sodM expressions. © 2017 Hainan Medical University